Tricin synthase (EC 2.1.1.175, ROMT-17, ROMT-15, HvOMT1, ZmOMT1) is an enzyme with systematic name S-adenosyl-L-methionine:tricetin 3',5'-O-dimethyltransferase.^[1][2] This enzyme catalyses the following chemical reaction

2 S-adenosyl-L-methionine + tricetin ${\displaystyle \rightleftharpoons }$ 2 S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin (overall reaction)

(1a) S-adenosyl-L-methionine + tricetin ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 3'-O-methyltricetin

(1b) S-adenosyl-L-methionine + 3'-O-methyltricetin ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin

The enzymes from Oryza sativa (ROMT-15 and ROMT-17) catalyses the stepwise methylation of tricetin to its 3'-mono- and 3',5'-dimethyl ethers.